Tumor necrosis factor-α-converting enzyme controls surface expression of c-kit and survival of embryonic stem cell-derived mast cells

Transmembrane metalloproteinases of the disintegrin and metalloproteinase ( ADAM) family control cell signaling interactions via hydrolysis of protein extracellular domains. Prior work has shown that the receptor tyrosine kinase, c- Kit ( CD117), is essential for mast cell survival and that serum levels of c- Kit increase in proliferative mast cell disorders, suggesting the existence of c- Kit shedding pathways in mast cells. In the present work, we report that tumor necrosis factor alpha- converting enzyme ( TACE; ADAM- 17) mediates shedding of c- Kit. Stimulation of transfected cells with phorbol 12- myristate 13- acetate ( PMA) induced metalloproteinase- mediated release of c- Kit ectodomain, which increased further upon TACE overexpression. By contrast, TACE-deficient fibroblasts did not demonstrate inducible release, thus identifying TACE as the metalloproteinase primarily responsible for PMA- induced c- Kit shedding. Surface expression of c- Kit by the human mast cell- 1 line decreased upon phorbol- induced shedding, which involved metalloproteinase activity susceptible to inhibition by tissue inhibitor of metalloproteinase ( TIMP)- 3. To further explore the role of TACE in shedding of c- Kit from mast cells, we compared the behavior of mast cells derived from murine embryonic stem cells. In these studies, PMA decreased surface c- Kit levels on mast cells expressing wild- type ( +/ +) TACE but not on those expressing an inactive mutant ( Delta Zn/ Delta Zn), confirming the role of TACE in PMA- induced c- Kit shedding. Compared with TACE (+)/ (+) cells, TACE(DeltaZn/DeltaZn) mast cells also demonstrated decreased constitutive shedding and increased basal surface expression of c- Kit, with diminished apoptosis in response to c- Kit ligand deprivation. These data suggest that TACE controls mast cell survival by regulating shedding and surface expression of c- Kit.